Mr Graham on Water as a Constituent of Salts. 31 1 



a warm solution, was found to contain three atoms of water. It 

 is likewise known to be deposited from a boiling solution with 

 only one atom of water, namely, the saline atom. We have, 

 therefore, sulphates of this class with no water of crystallization, 

 and with two, four, and six atoms. 



The sulphate of manganese and potash did not crystallise on 

 mixing the solutions of its constituents. The sulphate of man- 

 ganese and soda was obtained in analogous circumstances with 

 the sulphate of copper and soda, but was not examined. 



Sulphate of Iron with Saline Water : FeSH-f-H c . Sulphate of 



Iron. 



Of the seven atomic proportions of water which the crystals 

 contain, 5.48 proportions were lost in vacuo over sulphuric acid ; 

 and six proportions at 238°, and probably at lower temperatures. 

 The saline atom of water is retained by this salt at so high a 

 temperature as 535°. But the salt can be made perfectly anhy- 

 drous, with proper caution, without appreciable loss of acid. 



Sulphate of Iron with Sulphate of Potash : FeS(KS)+ H 6 . Sul- 

 phate of Iron and Potash. 



A specimen of this salt was made anhydrous by a sandbath 

 heat, which was found not to affect the saline atom of water of 

 the preceding compound. 



Sulphate of nickel was found to correspond closely with sul- 

 phate of iron in the temperatures at which it lost its water of 

 crystallization, and also its saline water. And in the case of both 

 of the compounds of these salts with sulphate of potash, a consi- 

 derably higher temperature was required to render them perfect- 

 ly anhydrous, than in the case of the corresponding double salt 

 of zinc. 



